A standard gas stove has an upper cooktop panel that is formed either of sheet metal or ceramic and that is provided with a plurality of burners. Each burner comprises a burner holder that is mounted underneath the cooktop panel and that is provided with a nozzle connected to a source of propane or butane, a burner head that is mainly above the cooktop panel and that diverts the gas from the nozzle normally into an annular array of jets, and a rack that fits over the head and that is intended to support a cooking utensil. A spark-type electrical igniter is also normally provided at each burner.
The rack normally is fitted with formations made in the cooktop panel. When the panel is made of sheet metal, it is relatively easy to provide appropriate seats for centering fingers on the rack, but when the panel is of ceramic, which is much more difficult to shape and machine, such centering formations are more difficult or impossible to provide. Thus the rack can slide about or be quite difficult to position accurately.
In addition the overall thickness of the cooktop panel varies considerably. When made of enameled steel it is quite thin, and when made of ceramic it is much thicker. In addition due to the difficulty of forming mounting holes in ceramic, the hole in the panel through which the burner extends is normally made larger in ceramic so that screws securing the head to the holder can pass through it, while with a metal panel it is easy to form separate holes for the mounting screws. it is therefore necessary to provide different burner constructions to accommodate the different panel thicknesses as well as the different layout of the mounting screws.
The burners typically vary in size, mainly in diameter. A large burner can in principle have, however, the same support as a small burner and merely needs a larger head and nozzle of greater flow cross section. Due to the larger head, it is necessary to provide the igniter at a different spacing from the center and, since the igniter is mounted on the holder, it has to be spaced differently from the center of the holder for burners of different sizes. Thus using the same holder is normally impossible and it is necessary to provide a separate holder for each burner size.
With many standard systems, large burners are somewhat taller than small burners. Thus a pot sits somewhat higher on a taller burner. This not only creates a nonuniform and unattractive appearance, but makes it impossible to set a cooking utensil, for instance a large kettle, on two adjacent burners of different size.